The incidence of malignant melanoma is increasing worldwide at rates that have been reported to be between 3 and 7 percent. In the United States, the incidence of melanoma is rising faster than any other malignancy. The overall goal of this project is to evaluate whether gene expression profiling can provide additional diagnostic and prognostic information for patients with malignant melanoma. Despite decades of attempts to identify clinical and histological features that would be useful in predicting which lesions were going to metastasize, only limited success can be claimed. The measured thickness (the Breslow measurement) and the presence or absence of ulceration are the strongest predictors of outcome for localized disease. The identification of patients with a high risk of metastasis is important for the surgical management of the patient as well as to determine which patients should be admitted to clinical trials of adjuvant agents as these become available. A comprehensive knowledge of the genes expressed by melanoma may be helpful in management of these patients. The specific aims are as follows: 1. To use genome-wide gene expression using microarray technology of human metastatic melanoma and congenital nevi in tissue specimens to identify candidates for accurate prognostication of melanoma patients with localized disease (Stages I and II). 2. Develop in situ hybridization assays for the candidate genes identified in Specific Aim 1. The assays will be validated both on from the tissues used in Specific Aim 1 as well as specimens from additional patients. 3. In situ hybridization will be utilized to examine tissue sections of primary melanomas. The pattern of involvement of the primary tumors will be correlated with clinical outcome. The results will be correlated with known prognostic factors to determine if the information provides additional prognostic information.